Field of the Invention
The present invention relates to an optical device wafer processing method for dividing an optical device wafer into individual optical devices such as light emitting diodes and laser diodes along a plurality of crossing division lines, the optical device wafer being composed of a single crystal substrate such as a sapphire (Al2O3) substrate and a silicon carbide (SiC) substrate and a light emitting layer formed on the front side of the single crystal substrate, the optical device wafer being partitioned by the division lines to define a plurality of separate regions where the optical devices are respectively formed.
Description of the Related Art
In an optical device fabrication process, a light emitting layer composed of an n-type nitride semiconductor layer and a p-type nitride semiconductor layer is formed on the front side of a single crystal substrate such as a sapphire (Al2O3) substrate and a silicon carbide (SiC) substrate. The optical device wafer is partitioned by a plurality of crossing division lines to define a plurality of separate regions where a plurality of optical devices such as light emitting diodes and laser diodes are respectively formed, thus constituting an optical device wafer. The optical device wafer is cut along the division lines to thereby divide the plural separate regions where the optical devices are formed from each other, thus obtaining the individual optical devices as chips.
As a method of dividing an optical device wafer along the division lines, there has been tried a laser processing method of applying a pulsed laser beam having a transmission wavelength to the wafer along the division lines in the condition where the focal point of the pulsed laser beam is set inside the wafer in a subject area to be divided. More specifically, this wafer dividing method using laser processing includes the steps of applying a pulsed laser beam having a transmission wavelength to the wafer from one side of the wafer along the division lines in the condition where the focal point of the pulsed laser beam is set inside the wafer to thereby continuously form a modified layer inside the wafer along each division line and next applying an external force to the wafer along each division line where the modified layer is formed to be reduced in strength, thereby dividing the wafer into the individual optical devices (see Japanese Patent No. 3408805, for example).
As another method of dividing an optical device wafer along the division lines, there has been put into practical use a technique including the steps of applying a pulsed laser beam having an absorption wavelength to the wafer along the division lines to thereby form a laser processed groove along each division line by ablation and next applying an external force to the wafer along each division line where the laser processed groove is formed as a break start point, thereby breaking the wafer along each division line (see Japanese Patent Laid-open No. Hei 10-305420, for example).